Market data recovery

ABSTRACT

Networks, systems and methods for recovering data messages from a market data stream and for building a book for a financial instrument are disclosed. An out-of-band data stream related to an as-of state of the market for one or more financial instruments is distributed parallel to a stream of market data for the financial instrument. The as-of data stream is referenced to the financial according to a unique identifier of the messages of the market data stream. The as-of data for a financial instrument may be provided at periodic rate that may be varied according to one or more factors.

This application claims priority to U.S. Provisional Application No.60/948,666, entitled “Market Data Recovery” filed Jul. 9, 2007, thedisclosures of which is expressly incorporated herein by reference inits entirety.

TECHNICAL FIELD

The present invention relates to distribution of data, and particularlyto recovery of streaming market data.

DESCRIPTION OF RELATED ART

Financial data, often referred to as market data, is typicallydistributed to a vast number of recipients. The market data may bedistributed or transmitted as a constant stream of consecutive messages.The consecutive messages may include information related to changes inthe market for a financial instrument or investing vehicle, such as suchas securities, commodities, equities derivatives and the like. Themarket data may relate to new orders entering a market, pending ordersin the market, cancelled orders, executed transactions, and other datarelated to market conditions. The messages may also include informationfrom which a current state of the market, or portion of the market, maybe derived.

The market data may be distributed using a data transmission protocol.One type of protocol, referred to as User Datagram Protocol (UDP)multicast architecture, uses a multi-feed efficient message delivery ofmarket data messages. In the market data applications, streams of dataare provided from an originator, such as an exchange, to recipients ofthe market data over a dedicated market data pipe, such as a T1 line.The pipe may include data transmissions for one or more financialinstruments or investing vehicles. The messages are sent as streams ofappropriately sized consecutive packets or messages that may bedetermined by a maximum transmission unit (MTU) size of a data linklayer of the network. The resulting packets are delivered through to areceiving module at a recipient end. Each packet may have a sequencenumber that may be used to identify each message received at therecipient and the order in which the messages are processed at thereceiving end.

The module at the recipient end may recognize when transmitted messagesmay not have been received. Lost messages or gaps in the stream of datamessages may be identified from the sequence numbers of the receivedmessages. Lost messages may be recovered through a process where therecipient identifies lost messages to the sender. After receivingrequests for lost messages, the sender may aggregate requests in aretransmission.

The retransmission of the data may be provided using a TransmissionControl Protocol of the Internet Protocol suite, (TCP/IP) where therequesters listen to the retransmitted messaged for the missing data.For example, if recipient 1 has not received messages 20-50 andrecipient 2 has not received 48-52, the sender may aggregate the tworequests and re-transmit messages 20-52. Recipient 2 will need to listento all messages before receiving the desired replacement transmission.

In another example, a new-comer to the market may not be able toidentify the current state of the market because a current market datastream does not include a reference point for the changes in the marketreflected in the market data stream.

Therefore, there exists a need for systems, methods and/or apparatusesto address the above concerns.

BRIEF SUMMARY

By way of introduction, market data recovery systems, apparatuses,and/or methods may be achieved by one or more devices, networks, and/orprocesses for distributing, communicating, transmitting, broadcasting,multicasting, storing, submitting, receiving, circulating, entering,managing, administering, and/or presenting market data.

The market data recovery system, method and/or apparatus addresses theimpact of missing data messages in a received market data stream, andtechniques for recovering the state of the market, or the “Order Book”in any particular instrument when messages in a data stream may havebeen missed and/or disaster recovery scenarios. The invention may allowrebuilding of the state of the market without having received all marketdata messages in a single market data feed. The market data recoverysystem, method and/or apparatus may also allow late joiners to a marketto rebuild a book where price updates were previously provided in amarket and to make an accurate assessment of the current state of themarket.

The foregoing summary is provided only by way of introduction. Thefeatures and advantages of aspects of the invention may be realized andobtained by the instrumentalities and combinations pointed out in one ormore of the claims. Nothing in this section should be taken as alimitation on the claims. Additional features and advantages will be setforth in the description that follows, and in part will be obvious fromthe description, or may be learned by practice of aspects of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of market data recovery systems are described with reference tothe accompanying drawings, in which components, features and integralparts that correspond to one another each have the same or similarreference number, wherein:

FIG. 1 shows a computerized system that may be used with animplementation of market data recovery in accordance with aspects of theinvention;

FIG. 2 shows a system for distributing market data in accordance withaspects of the invention; and

FIG. 3 shows a flow chart for a method for recovering market data inaccordance with aspects of the invention.

DETAILED DESCRIPTION

Market data recovery systems in accordance with aspects of the inventionmay take physical form in certain parts and steps, embodiments of whichwill be described in detail in the following description and illustratedin the accompanying drawings that form a part hereof. Market datarecovery systems, methods and apparatuses may be achieved in manydifferent forms, formats, and designs and should not be construed aslimited to the exemplary embodiments set forth herein.

A match engine may provide as output, among other things, dataassociated with market events and conditions. The output from the matchengine may be provided to a market data routing module including amarket data router. The market data routing module may be one or morecontrollers, processors, servers, gateways, computer combinationsthereof and the like. The market data router may output at least onemarket data channel. The market data channel distributes market datagenerally in the form of streaming, or a substantially constant streamof data messages. The market data channel may distribute the informationfor one or more financial instruments or investment vehicles.

The out of band channel market data recovery module provides datarelated to a state of the book for an instrument or other investmentvehicle. The out of band channel resides outside of the actual marketdata stream channel. The out of band channel market data recovery moduleprovides the as-of state of the book for a specified point in time. Thestate of the book is periodically updated and resent or retransmitted ata predetermined or configurable rate. The rate may be adjusted on one ormore factors, including the volume or relative for the product, the timeof day, volume for other products and the like.

The data may include an as-of sequence number, which may be used toprovide a reference point to the streaming data distributed on themarket data channel. The as-of data and sequence number providesinformation related to the state of the market at a point in time andmay correlate to the sequence number of the data provided on the marketdata channel. A recipient of the data on the market data channel may beable to rebuild all or a portion of a book by using the as-of data fromthe out-of-band channel with the streaming data from the market datachannel.

Referring to FIG. 1, various aspects of the present invention may beimplemented with computer devices and networks configured to allow usersto exchange trading information. In illustrative embodiments, systems,methods and apparatuses for administering, communicating, managing,placing, entering, receiving, matching, clearing, presenting, listingand/or confirming orders for bundled financial instruments may beachieved in many different forms, formats, and designs. Embodiments maytake the form of one or more devices, systems, distributed networks,data processing systems, and/or processes and should not be construed aslimited to the illustrative embodiments set forth herein. Anillustrative trading network environment for implementing tradingsystems and methods is shown in FIG. 1.

An exchange computer system 100 receives orders and transmits marketdata related to orders, trades and related information. Exchangecomputer system 100 may be implemented with one or more mainframes,servers, gateways, controllers, desktops or other computers. Theexchange computer system 100 may include one or more modules, databases,and other components, such as those illustrated in FIG. 1. An electronictrading system, such as the Globex® trading system, may be associatedwith an exchange 100. In such an embodiment, the electronic tradingsystem includes a combination of globally distributed computers,controllers, servers, networks, gateways, routers, databases, memory,and other electronic data processing and routing devices.

The trading system may include a trading system interface having devicesconfigured to route incoming messages to an appropriate devicesassociated with the trading system. The trading system interface mayinclude computers, controllers, networks, gateways, routers and otherelectronic data processing and routing devices. Orders that are placedwith or submitted to the trading system are received at the tradingsystem interface. The trading system interface routes the order to anappropriate device.

A match engine module 106 may match bid and offer prices for ordersconfigured in accordance with aspects of the invention. Match enginemodule 106 may be implemented with software that executes one or morealgorithms for matching bids and offers for bundled financialinstruments in accordance with aspects of the invention. The matchengine module and trading system interface may be separate and distinctmodules or component or may be unitary parts. Match engine module may beconfigured to match orders submitted to the trading system. The matchengine module may match orders according to currently known or laterdeveloped trade matching practices and processes. In an embodiment, bidsand orders are matched on price, at on a FIFO basis. The matchingalgorithm also may match orders on a pro-rata basis or combination ofFIFO and pro rata basis. Other processes and/or matching processes mayalso be employed.

Furthermore, an order book module 110 may be included to compute orotherwise determine current bid and offer prices. The order book module110 may be configured to calculate the price of a bundled financialinstrument based on an average price of the plurality of short-termfinancial instruments from the prior trading day's close. The averagemay be a weighted to reflect the percentage of the total bundle that aparticular financial instrument constitutes. Moreover, a trade database108 may be included to store information identifying trades anddescriptions of trades. In particular, a trade database may storeinformation identifying or associated with the time that an order wasexecuted and the contract price. The trade database 108 may alsocomprise a storage device configured to store at least part of theorders submitted by electronic devices operated by traders (and/or otherusers). In addition, an order confirmation module 132 may be configuredto provide a confirmation message when the match engine module 106 findsa match for an order and the order is subsequently executed. Theconfirmation message may, in some embodiments, be an e-mail message to atrader, an electronic notification in one of various formats, or anyother form of generating a notification of an order execution.

A market data module 112 may be included to collect market data andprepare the data for transmission to users. In addition, a riskmanagement module 134 may be included to compute and determine a user'srisk utilization in relation to the user's defined risk thresholds. Anorder processing module 136 may be included to receive data associatedwith an order for a financial instrument. The module 136 may decomposedelta based and bulk order types for processing by order book module 110and match engine module 106. The order processing module 136 may beconfigured to process the data associated with the orders for financialinstruments.

A user database 102 may include information identifying traders andother users of exchange computer system 100. Such information mayinclude user names and passwords. A trader operating an electronicdevice (e.g., computer devices 114, 116, 118, 120 and 122) interactingwith the exchange 100 may be authenticated against user names andpasswords stored in the user database 112. Furthermore, an account datamodule 104 may process account information that may be used duringtrades. The account information may be specific to the particular trader(or user) of an electronic device interacting with the exchange 100.

The trading network environment shown in FIG. 1 includes computer (i.e.,electronic) devices 114, 116, 118, 120 and 122. The computer devices114, 116, 118, 120 and 122 may include one or more central processors,or controllers, that control the overall operation of the computer. Thecomputer devices 114, 116, 118, 120 and 122 may include one or moresystem buses that connect the central processor to one or morecomponents, such as a network card or modem. The computer devices 114,116, 118, 120 and 122 may also include interface units and drives forreading and writing data or files. Depending on the type of computerdevice, a user can interact with the computer with a keyboard, pointingdevice, microphone, pen device or other input device. Computer device114 is shown communicatively connected to exchange computer system 100.Exchange computer system 100 and computer device 114 may be connectedvia a T1 line, a common local area network (LAN) a wirelesscommunication device or any other mechanism for communicativelyconnecting computer devices.

Computer (i.e., electronic) devices 116 and 118 are coupled to a localarea network (“LAN”) 124. LAN 124 may have one or more of the well-knownLAN topologies and may use a variety of different protocols, such asEthernet. Computers 116 and 118 may communicate with each other andother computers and devices connected to LAN 124. Computers and otherdevices may be connected to LAN 124 via twisted pair wires, coaxialcable, fiber optics or other media. Alternatively, a wireless personaldigital assistant device (PDA) 122 may communicate with LAN 124 or theInternet 126 via radio waves. PDA 122 may also communicate with exchangecomputer system 100 via a conventional wireless hub 128. As used herein,a wireless PDA 122 includes mobile telephones and other devices thatcommunicate with a network via radio waves. FIG. 1 also shows LAN 124connected to the Internet 126. LAN 124 may include a router to connectLAN 124 to the Internet 126. Computer device 120 is shown connecteddirectly to the Internet 126. The connection may be via a modem, DSLline, satellite dish or any other device for communicatively connectinga computer device to the Internet.

One or more market makers 130 may maintain a market by providingsubstantially constant bid and offer prices for a financial instrument,such as a derivative or security, to exchange computer system 100.Exchange computer system 100 may also exchange information with othertrade engines. Numerous additional computers and systems may be coupledto exchange computer system 100. Such computers and systems may includeclearing, regulatory and fee systems.

The operations of computer devices and systems shown in FIG. 1 may becontrolled by computer-executable instructions stored oncomputer-readable medium. Embodiments also may take the form ofelectronic hardware, computer software, firmware, including objectand/or source code, and/or combinations thereof. Embodiment may bestored on computer-readable media installed on, deployed by, residenton, invoked by and/or used by one or more data processors, controllers,computers, clients, servers, gateways, networks of computers, and/or anycombinations thereof. The computers, servers, gateways, may have one ormore controllers configured to execute instructions embodied as computersoftware. For example, computer device 116 may includecomputer-executable instructions for receiving order information from auser and transmitting that order information to exchange computer system100. In another example, computer device 118 may includecomputer-executable instructions for receiving market data from exchangecomputer system 100 and displaying that information to a user.

An embodiment may include software stored and executed on an electronicdevice such as one or more traders terminals, connected to a matchserver having electronic components configured to carry out instructionsaccording to a computer program stored on a computer-readable storagemedium, such as a memory, hard disk, CD-ROM, optical storage device,magnetic storage device and/or combinations thereof to match orders forbundled financial instruments. The electronic device may be a computingdevice having a programmable controller or processor. For example theelectronic device may be a personal computer, laptop or handheldcomputer, tablet pc and like computing devices having a user interface.The electronic device may be a dedicated function device such aspersonal communications device, a portable or desktop telephone, apersonal digital assistant (“PDA”), remote control device, personaldigital media system and similar electronic devices.

Additional servers, computers, handheld devices, personal digitalassistants, telephones and other devices may also be connected toexchange computer system 100. Moreover, the topology shown in FIG. 1 ismerely an example and that the components shown in FIG. 1 may beconnected by numerous alternative topologies.

Aspects of market data recovery may be implemented with electroniccomputing devices and/or networks (e.g., Internet, telecommunicationnetworks, local area networks, wide area networks, private proprietarynetworks, etc.). The electronic computing devices may be configured toallow users to exchange and receive trading information. An illustrativetrading network environment for receiving, processing, and restoringmarket data for financial instruments and methods thereof in accordancewith various aspects of the invention are shown in FIG. 1.

FIG. 2 illustrates a system for distributing market data in accordancewith various aspects of the invention. A market data routing module 208comprising a market data router 210 is communicatively coupled with amatch engine (not shown). The market data router 210 receives a marketdata feed from the match engine 206. The market data router 210distributes the data stream on a market data channel to a remote tradingsystem 202. In one example, the market data may be distributed in asubstantially constant stream of consecutive data messages. The marketdata stream may be distributed within the electronic trading exchange100 and/or outside of the electronic trading exchange 100.

In the illustrative embodiment of FIG. 2, the market data streamcomprises bid and ask prices of order for a financial instrument. Eachdata message in the market data stream may be identified by a unique asequence number tag. The messages may also include other identifiersknown to those of ordinary skill in the art. The sequence numberprovides a mechanism for recreating the market data stream should theremote trading system 202 become disconnected from the exchange 100.

In accordance with aspects of the invention, a snapshot message maycomprise multiple levels (e.g., five levels deep) of bid and ask pricesfor a particular financial instrument. The snapshot message may alsoinclude the quantity, instrument symbol (e.g., GEM7, etc.) and uniquesequence identifier. A market data recovery module (e.g., an out-of-band(OOB) market data recovery module 214) may generate snapshot messages216 using market data, and distribute the snapshot message 216 to aremote system 202. The data recovery module 214 may transmit out-of-bandfor numerous reasons, including, but not limited to reducing latency.

In addition, the OOB data recovery module 214 may transmit other typesof messages to a remote system 202. For example, an out of band channelmay comprise incremental market data messages 220, snapshot messages222, and/or dictionary messages 224. Dictionary messages may be used todisseminate instrument definitions (e.g., similar to RLC MO/MU formattedmessages known to those of skill in the art). The OOB data recoverymodule 214 may transmit message via one or more OOB channels usingmulticasting technology. One skilled in the art will appreciate thatmulticasting and UDP technologies may be useful in distributing messagesin the described architectures.

The snapshot messages may be distributed using an as-of data channel.Such an as-of channel may periodically transmit data related to thestate of a book. The as-of data channel may provide the data related toone or more books. The rate at which the as-of data is provided may bepredetermined and may be variable based on one or more factors. A uniquesequence identifier may be used to synchronize the in-band market data(e.g., the streaming market data) with the out-of-band data. The as-ofdata may be used in such a synchronization process.

In addition, in accordance with aspects of the invention, an orderentry/receiving device 202 is disclosed comprising a memory 204 and aprocessor 206. The memory 204 may contain a computer-readable mediumstoring computer-executable instructions for execution by the processor206. The computer-readable medium may contain instructions forperforming one or more of the method steps described in this disclosureand any incorporated by reference. The instructions may be embodied, inone example, as computer software running on a personal computerbehaving as an order entry/receiving device 202. The software maygenerate a graphical user interface for presentation on a visual displayin order to permit a user to create an order and receive market andother data.

The order entry/receiving device 202 may comprise an order receivingcomponent (not shown) configured to receive data (e.g., in-band data andout-of-band data) associated with a financial instrument. In oneexample, the order receiving component may be an electronic component(e.g., a modem, network card, input/output port) on device 202.Alternatively, the order receiving component may be a buffer in memory204 for initially receiving incoming data. In another example, the orderreceiving component may be configured to register to receive datamessage for a particular financial instrument (e.g., out-of-band datafor an order book in data recovery mode.) Furthermore, the device 202may comprise an order storage component (e.g., memory 204) configured tostore the data of the financial instrument. In one example the orderstorage component may be cache memory for caching incoming market dataduring recovery mode. In addition, the device 202 may comprise a bookrebuilding component configured to rebuild the order book. In oneexample, the rebuilding component may be implemented ascomputer-executable instructions on a computer-readable medium that iscapable of performing the rebuilding process, including (whereappropriate) the various rebuilding approaches.

FIG. 3 shows a flow chart for a method for recovering market data inaccordance with aspects of the invention. In step 302, the tradingsystem 202 may receive a substantially constant stream of consecutivedata messages. Each data message may have a unique identifier and beassociated with a market event for a financial instrument. In step 304,the trading system 202 may periodically receive a data messages relatedto the state of the market for the financial instrument. Moreover, thestate of the market may be referenced to at least on unique identifier.In step 306, the trading system 202 may determine whether the order bookrequires rebuilding due to a connectivity failure with an exchange 100.If a rebuilding is desired, in step 308, the trading system 202 mayrebuild the order book for the financial instrument according to theconstant stream of consecutive data messages and the data messagesrelated to the state of the market.

The rebuilding process may be performed using one or more approaches.For example, a natural refresh approach may be used to refresh theomitted market data in the appropriate order books. One of skill in theart will appreciate that a natural refresh approach may be desirable incertain circumstances. For instance, a natural refresh approach may notbe desirable for illiquid financial instruments. In another example, aconcurrent processing approach may be used to synchronize data messagesreceived from an OOB market data recovery module with cached market datamessages received from a market data routing module. The OOB messagesand in-band messages may be synchronized using an as-of sequence numberassociated with a snapshot message. The snapshot message may be used toshow the state of a book as of a certain sequence number.

Moreover, in such approaches a liveness criteria may be implemented toremove cached data messages (e.g., in-band market data message) thathave become obsolete. As explained earlier, using the as-of sequencenumber, a snapshot message may inserted into the cached data stream atthe appropriate position. As a result, cached data messages prior to theas-of sequence number associated with the snapshot can be dropped.Meanwhile data messages following the as-of sequence number may beapplied to the order book as updates. The rebuilding approach used maybe based on one or more predetermined criteria, such as increasingperformance, decreasing processing time, reducing cache memory usage,etc. One of skill in the art will appreciate that one or more, orcombination thereof, of the aforementioned approaches, and otherapproaches known to those of skill in the art, may be used in accordancewith aspects of the invention.

In another example, the trading system 202 may register (in step 310)with an exchange 100 (or other entity capable of distributing theappropriate data) to receive messages related to the state of the marketfor the financial instrument (e.g., snapshot messages, etc.). The datamessages may be sent out-of-band, and the trading system 202 mayspecifically request which out-of-band channel it desires. For example,the trading system 202 may register to receive that recovery datamessages (e.g., snapshot messages, etc.) for a particular financialinstrument or group of financial instruments out-of-band. As such, thebandwidth consumed and latency is more efficient. In addition, thetrading system 202 may cache consecutive data messages in a cache instep 312. The consecutive data messages may be received as asubstantially constant stream of market data.

Additional servers, computers, handheld devices, personal digitalassistants, telephones and other devices may also be connected toexchange computer system 100. Moreover, the topology shown in FIG. 1 ismerely an example and that the components shown in FIG. 1 may beconnected by numerous alternative topologies. Embodiments in accordancewith aspects of the invention may take the form of one or more devices,systems, distributed networks, data processing systems, processes,electronic hardware, computer software, firmware, including objectand/or source code, and/or combinations thereof. Embodiments may bestored on computer-readable media installed on, deployed by, residenton, invoked by and/or used by one or more data processors, controllers,computers, clients, servers, gateways, networks of computers, and/or anycombinations thereof. The computers, servers, gateways, may have one ormore controllers configured to execute instructions embodied as computersoftware. Embodiment may be transmitted as a carrier signal from a firstelectronic device to another electronic device. The carrier signal, whenreceived at an electronic device and executed by a processor, mayprovide a means for event triggered trading in accordance with aspectsof the invention.

Various embodiments have been described and illustrated. However, thedescription and illustrations are by way of example only. Many moreembodiments and implementations are possible within the scope of thisinvention and will be apparent to those of ordinary skill in the art.The various embodiments are not limited to the described environments,and can be applied to a wide variety of activities.

It is intended in the appended claims to cover such changes andmodifications which fall within the true spirit and scope of theinvention. Therefore, the invention is not limited to the specificdetails, representative embodiments, and illustrated examples in thisdescription. Accordingly, the invention is not to be restricted exceptin light as necessitated by the accompanying claims and theirequivalents.

1. A computer-implemented system for updating market data, the systemcomprising: a data router configured to distribute a stream of marketdata, the stream of market data including consecutive messages eachhaving a unique identifier; and an out of band market data recoverymodule configured to periodically distribute data related to a state ofa market for at least one financial instrument at a predetermined rate,the state of the market being referenced to at least one message of thestream of market data according to the unique identifier for themessage, the data related to the state of the market comprising snapshotmessages.
 2. The system of claim 1 where the recovery module generatesthe data related to the state of the market according to the stream ofmarket data.
 3. The system of claim 1 where the recovery module isconfigured to distribute data related to the state of a market for afirst financial instrument at a first predetermined rate and a secondfinancial instrument at a second predetermined rate.
 4. The system ofclaim 3 where the first predetermined rate is substantially same as thesecond predetermined rate.
 5. The system of claim 3 where the firstpredetermined rate is less than the second predetermined rate.
 6. Thesystem of claim 3 where the first predetermined rate is variable.
 7. Thesystem of claim 1 where the data related to the state of a marketincludes information related to a plurality of investment vehicles anddefinition messages.
 8. The system of claim 1 where the recovery moduledistributes data using multicast broadcasting.
 9. A method forrecovering streaming data comprising: receiving a substantially constantstream of consecutive data messages, each having a unique identifier andassociated with a market event for a financial instrument; periodicallyreceiving a data messages related to a state of the market for thefinancial instrument, the state of the market being referenced to atleast one unique identifier; and rebuilding a book for the financialinstrument according to the consecutive data messages and theconsecutive data messages related to the state of the market.
 10. Themethod of claim 9, where the rebuilding includes a natural refreshapproach.
 11. The method of claim 9, where the rebuilding includes aconcurrent processing approach.
 12. The method of claim 9, where therebuilding includes automatically selecting one of a natural refreshapproach and a concurrent processing approach according to predeterminedcriteria.
 13. The method of claim 9, comprising: registering to receivethe data messages related to the state of the market for the financialinstrument; and caching the consecutive data messages in a cache, theconsecutive data messages received as a substantially constant stream.14. The method of claim 13, comprising removing the consecutive datamessages in the cache if a data message fails a liveness criteria, wherethe rebuilding includes a concurrent processing approach.
 15. Acomputer-readable medium comprising computer-executable instructions forperforming the method of claim
 9. 16. An order trading systemcomprising: an order receiving component configured to receive dataassociated with a financial instrument; an order storage componentconfigured to store the data of the financial instrument; and a bookrebuilding component configured to rebuild an order book for thefinancial instrument; wherein the data received by the order receivingcomponent comprises market data and out of band data associated with thefinancial instrument.
 17. The system of claim 16, where the datareceived by the order receiving component is associated with a uniqueidentifier.
 18. The system of claim 16, where the order receivingcomponent is further configured to register to receive data associatedwith a predetermined financial instrument.
 19. A market data recoverysystem comprising: means for distributing including consecutive messageseach having a unique identifier; means for periodically compiling astate of a market for a financial instrument; means for associating thestate of the market with at least one unique identifier; and means fordistributing the periodically compiled state of the market and theunique identifier.
 20. The system of claim 19, wherein the periodicallycompiling occurs at a predetermined interval